14: Many Liquids from One Bottle : (Contributed by John Kinsman)

14: Many liquids from one bottle: (contributed by John Kinsman)

Find five empty wine glasses - (or 100cm3 beakers) A to E and one empty wine bottle, preferably brown glass.

Dissolve potassium manganate VII (0.4g) – usually called potassium permanganate - in 100cm3 of 2M sulphuric acid and dilute this to 1 litre. Use this solution to fill the wine bottle. (POISON)

Have the wine glasses prepared as follows before the audience sees them.

A. Empty B. 1 cm3 of a solution of 25g of sodium thiosulphate in 100cm3 of water C. 1 cm3 of the sodium thiosulphate solution plus 3cm3 of a solution of 24g barium chloride in 100cm3 of water. (POISON) D. 3cm3 of the barium chloride solution. (POISON) E. 1cm3 of the sodium thiosulphate solution plus 3cm3 of a solution of 21g of sodium carbonate in 100cm3 of water.

(Sodium sulphate (IV) Na2SO3 (sodium sulphite) can, with some advantage, replace sodium thiosulphate – although if this is used it is necessary to add excess hydrochloric acid to the solution in C to prevent precipitation of the barium sulphate (IV). In this case no sulphur is produced when the solutions B,C & E are allowed to stand.)

In turn pour an estimated 100cm3 out of the bottle into the glasses in turn.

A will be ‘red wine’, B will be ‘water, C will be ‘milk, D will be ‘raspberry milk shake’ and D will be ‘fizzy lemonade’.

Risk Assessment

Everyone should appreciate that this is a chemical process in which the names of the solutions have been changed. All the liquids are poisonous and must not be drunk. Eye protection is still appropriate even if not strictly necessary. Make sure that any stock solutions are properly labelled and stored (Solutions of sodium thiosulphate are not stable for long-term storage and can support the growth of moulds.)

Barium chloride is a scheduled poison, although it is rendered harmless once excess sulphuric acid has been added from the ‘wine’ bottle.

Rinse out the ‘wine’ bottle immediately after use, and recycle or save for the next session. The wine glasses should be thoroughly washed and rinsed before re-use and will preferably be reserved for future chemical ‘experiments’.

30 Educational Context

This is certainly how some conjurors do it, but here is an opportunity to understand something of the process. It is necessary to stress that even if they look ‘interesting’, the liquids produced must not be tasted.

The decolourisation of acidified potassium manganate VII by reducing agents is a good test for reducing agents (SO2, H2S as well as Na2S2O3) although the actual chemistry is unlikely to be met before A-level. However, once we know about this the reaction can readily be ‘understood’.

A. No change B. Simple decolourisation (Mn2+ ions are formed and are almost colourless.) C. Decolourisation + white precipitate of barium sulphate (VI). D. Purple colour remains + white precipitate E. Decolourisation + generation of carbon dioxide by reaction between acid and carbonate.

(Remember it can be used as a conjuring trick - but it really is chemistry and not food science!)